Well it depends on your regulator. They have a max current rating that they can take without burning out. Look at the back of it to find out or tell us what make and model it is and we can google it.
How to connect the panels is also dependent on the regulator voltage ratings and the type. But generally you will wire extra panels in parallel so the current is increased if the regulator can take it. If the regulator is a MPPT type then you might wire in series if the voltage rating is OK.
Not only the voltage rating needs to be within spec to connect them in series, they also need to have the same Vmp and Imp to work together, otherwise the smaller panel will pull the other panel down to match it.
If the panels are identical and you have a quality MPPT controller, then simply connect the negative from panel 1 into the positive of panel 2 and the negative from panel 2 into the open negative connector that is wired down to the solar controller.
If the solar controller is a PWM type, check the cable size from the existing panel to the controller and from there to the battery. If this cable isn't a large enough conductor to carry more current then adding a panel in parallel to the existing wiring is a waste of time, money and effort. If the cable can't carry the additional current then it won't flow through to the controller or on to the battery, it will just cause the solar panel to heat up.
T1 Terry
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